Genomic fingerprinting is one of several methods for screening human genome to identify genetic alterations in cancer cells. Arbitrarily primed polymerase chain reaction (AP-PCR) is a PCR-based genomic fingerprinting method (1 ). In AP-PCR, a single oligonucleotide is used to initiate DNA synthesis from sites along the template with which it matches only imperfectly. PCR is performed under a low stringent condition in the initial five cycles to permit hybridization of arbitrary primers to various sequences dispersed throughout the human genome. This is followed by 30-35 cycles of PCR under high stringent condition, so that only the best matches of the initial annealing events are further amplified. By controlling the stringency of the initial cycles, 50-100 distinct DNA fragments can be amplified from the human genome by a single PCR. When those fragments are size fractionated by gel electrophoresis, a representative sample of cell genome is visualized by staining or autoradiography as a genomic fingerprint. Because of the arbitrary nature for designing a primer and the low stringent condition for hybridization of a primer, DNA fragments are simultaneously amplified from various chromosomal regions in a single PCR. By comparison of AP-PCR genomic fingerprints of DNA from tumors and normal tissues, deleted and amplified DNA sequences in cancer cells have been detected and cloned (2 -5 ). Intensities of deleted and amplified DNA fragments are decreased and increased, respectively, by AP-PCR.